Gas turbine engine thrust deflectors

ABSTRACT

The blocker flaps in the fan duct of a gas turbine ducted fan engine are mounted for simultaneous pivoting across the fan duct and movement bodily downstream thereof so as to attain the required throat area for the subsequently reversed flow of fan air through the reverser aperture in the fan cowl.

UllltEd States Patent [15] 3, Colley 51 Sept. 19, 1972 [5 GAS TURBINEENGINE THRUST [56] References Cited- DEFLECTORS UNITED STATES PATENTS[72] Inventor: Rowan Herbert Colley, Derby, En-

gland 3,603,090 9/ 1971 Billinger et al. ..60/229 Assigneez Rolls RoyceLimited, y, Em 3,608,3 l4 8/l969 Colley ..60/229 gland PrimaryExaminer-Carlton R. Croyle [22] Filed: April 1, 1971 AssistantExaminerRobert E. Garrett [21] AppL No; 130,417 Attorney-Cushman, Darby& Cushman [57] ABSTRACT [30] Foreign Application Priority Data Theblocker flaps m the fan duct of a gas turbme P 2, 1970 Great Brltam l 6ducted fan engine are mounted for simultaneous pivoting across the fanduct and movement bodily US- CL A downstream thereof so as to attain therequired throat [5 rea fo the ubsequently reversed flow of fan air Fleldof Search "v A, R, through the reverser aperture in the fan cowl.

' 3 Claims, 3 Drawing Figures GAS TURBINE ENGINE THRUST DEFLECTORS Thisinvention concerns a thrust reverser for gas turbine engines havingannular ducts through which the propulsive fluids flow to atmosphere.

In the past, considerable difficulty has been experienced in retainingefficient reversal of the propulsive fluids produced by gas turbineengines particularly engines of the type which have an annular fluidflow duct. One problem is that the radial dimension of the annular ductis small relative to the axial dimension required in the reversed fluidoutlet aperture which is provided in the cowl or casing, which cowl orcasing forms the outer wall of the duct. If the aperture could be madecompletely annular, with no obstructions therein, then in theory, anaperture having an axial length equal to the radial depth of the annulusshould be sufficient for the fluid to flow through when the annulus issuitably blocked against axial flow, thus the same means could be usedto alternately block the aperture and the annulus. However, a completelyannular aperture is not practicable, support members must extend acrossthe aperture axially of the engine so as to join those portions of thecowl which define the aperture and thus the aperture would be partiallyobstructed, the effect being interalia, to choke the aperture, losereverse thrust efficiency and create undesirable back pressures on thefluid compressor. Thus, the aperture must be made bigger in area, thanthe annular duct.

A plurality of axially aligned blocker flaps have been used, some ofwhich are adapted to move when reversal is required so as to leavespaces between themselves for the fluid to flow through and theremainder moved to block the annulus. These mechanisms are unavoidablycomplicated and therefore difficult to construct so as to ensurereliability. Moreover they normally incur weight penalties and createsome obstruction even though moved, thus reducing the throat. Moreoverblocker flaps which fold upon themselves so as to change their shapewhen moved to a blocking position have been used, but hereto, difficultyhas been experienced in obtaining the correct throat area between theduct and aperture so as to avoid choking.

It is thus an object of the present invention to provide blockerapparatus of much simpler and lighter construction than priorconstructions, which is capable of alternately blocking both theaperture and the relatively small annulus and which is at least asefficient as said prior constructions.

Accordingly the present invention comprises a fan cow] for a gas turbineengine which cowl includes at least one axially translating portionwhich when translated in one direction, uncovers or forms an aperture insaid cowl, and at least one pivotable blocker flap which, when pivotedin one direction further uncovers or further forms said aperture, the atleast one blocker flap having a pivot axis which itself is mounted forat least arcuate movement when said blocker flap is caused to pivot.

Preferably the translatable portion of the cowl is connected to the atleast one blocker flap to cause movement thereof when said translationoccurs.

Preferably the cowl is adapted to surround a fan rotatably and coaxiallymounted on a gas turbine engine.

Alternatively the cowl may form part of a jet pipe of a gas turbineengine having an exhaust bullet mounted at or adjacent the nozzle of thegas turbine engine, the cowl and nozzle forming an annular fluid flowduct therebetween.

The invention will now be described with reference to the accompanyingdrawings in which:

FIG. 1 is a diagrammatic view of a gas turbine engine having a ductedfan.

FIG. 2 is an enlarged axial part section through the engine and ductedfan.

FIG. 3 is a pictorial view of the blocker flap of FIG.

In FIG. 1 a gas turbine ducted fan engine is indicated generally by thenumeral 10. The engine comprises a compressor, combustion equipment, anexpansion turbine and an exhaust nozzle 12 of which only the latter isshown.

A stage of fan blades 14 is rotatably and coaxially mounted at theupstream end of the engine, upstream that is, relative to the flow offluids through the engine.

The fluid is of course, ambient air, some of which is mixed with fueland burnt, returning to atmosphere .via the turbine and nozzle 12 in theform of hot gases and the remainder passing through the fan 14 toby-pass the gas turbine portion and return to atmosphere via a fan duct16 and nozzle 18.

The outer wall of the fan duct 16 is formed by the inner wall of the fancowl 20. Cowl 20 comprises upstream portion 22, downstream portion 24rigidly joined to upstream portion 22 by a plurality of axiallyextending, circumferentially spaced ribs 26 (Fig. 2) and a mid-portion28 which is translated axially of the engine so as to selectivelyuncover an aperture 30 defined by upstream and downstream portions 22and The radially inner end (radially that is, relative to the engineaxis) of aperture 30 is closed by a plurality of blocker flaps 32 whichare arranged peripherally of the cowl and which have fillet flaps 34pivotally attached thereto for pivoted movement about pivot axes 36.

The blocker flaps are each mounted at their downstream ends for bothpivot movement and for movement bodily in an axial direction. Thepivoted movement takes place about an axis 38 and, at the same time,movement bodily occurs in an axial direction by virtue of the blockerflaps having roller members 40 which contain axes 38, roller members 40being mounted in track members 42 which are fixed to the downstreamportion 24 of cowl 22.

The roller members 40 are rotatably mounted on ribs 44 with which eachblocker flap 32 is provided. Ribs 44 extend beyond the downstream end ofthe blocker flaps and the ribs own downstream extremity are pivotallyconnected to links 46. Links 46 are in turn connected for pivoting aboutan axis 48 which has a fixed location within downstream portion 24 ofcowl 22.

Track members 42 are curved in a substantially radially outwardlydirection at their upstream ends and when blocker flaps 32 are in thefull line position shown in Fig. 2 wherein they close the inner end ofaperture 30, rollers 40 lie at the upstream end thereof. Moreover,reference to Fig. 2 shows translating portion 28 of cowl 22 to becovering the outer end of aperture 30.

An engine as described herein is particularly suited to power aircraftand its operation when so utilized will now be described:

On touchdown of the aircraft, the pilot actuates rams 50 or the like,which are connected to translating portion 28 or cowl 22. The ramsextend and push portion 28 downstream. This movement is transmitted vialinks 52 to blocker flaps 32 which are thus caused to move bodily in adownstream direction by movement of roller members 40 along first thecurved portion and then the straight portions of tracks 42.

Pivoting of flap members 32 is brought about by their connection withlink 46 which pivots about axis 48 and thus lifts the downstream end offlaps 32, tipping the upstream ends thereof inwards towards the outercasing 54 of the gas turbine portion of the engine as shown in dottedlines in FIG. 2. Fan duct 16 is thus blocked in the axial direction andfan air will be deflected radially outwardly through aperture 30 byblocker flaps 32. If it is required to deflect the fan air in anupstream direction on leaving the aperture 30 so as to provide thrustreversal, guide vanes 56 may be provided in the aperture and are soshaped and positioned as to effect the desired deflection.

As can be seen in FIG. 2 the length of aperture 30 is greater than theradial depth of annulus 16 by the amount b. Blocker flaps 32 extend thefull axial length of aperture 30 and, if the flaps were pivoted about afixed axis at A at the downstream end of aperture 30, then the throat Bof the passage thus formed would be of insufficient area for the fan airto flow through without choking. However, simultaneous pivoting andbodily movement of the blocker flaps to the position shown is dottedlines in Fig. 2 increases the throat to the value C' which is sufficientto obviate choking. Thus the flaps have achievedthe blocking alternatelyof the aperture and duct without changing shape and on blocking theannulus 16, ,without choking the throat of the passage through which thefan air is deflected so as to pass to aperture 30. Moreover, while anumber of flaps 32 will be required to be spaced peripherally of theinner end of aperture 30 so as to completely close it when thrustreversal or deflection is not required, each blocker flap is of onepiece construction and is of sumcient length to axially span aperture30. The one piece construction permits a light weight, simple structureof great rigidity to be utilized.

The invention is described herein in connection with the fan cowl of agas turbine ducted fan engine, but, as is diagrammatically illustratedin FIG. 1 the invention could be applied to a gas turbine engine whichdoes not have a ducted fan. In this arrangement, the jet pipe wall 62and an exhaust bullet-64 would combine to form an annulus 66 and thereverser or deflector apparatus described herein would be positioned asindicated by numeral 68.

I claim:

1. A gas turbine ducted fan engine cowl of double wall constructioncomprising an outer wall including an annular, axially translatableportion, and an inner wall including a plurality of pivotable flapsspaced circumferentially of said inner wall, each flap having a pair ofrollers at its downstream end, aplurality of pairs of guide tracks fixedbetween the walls of the cowl and s aced c'rcumferentiall thereof andcans for transl ting said annular por tion axially oi the cowl, and

wherein said flaps have their rollers located in respective guide tracksso as to be pivoted about the rollers axes, whilst the rollers aremovable along said guide tracks so as to bodily displace said flapsaxially of the cowl.

2. A gas turbine ducted fan engine cowl as claimed in claim 1 whereinsaid annular translatable portion and said flaps are interconnected forsimultaneous movement in their respective directions.

3. A gas turbine ducted fan engine cowl as claimed in claim 1 whereinsaid means for translating said annular portion comprises rams.

1. A gas turbine ducted fan engine cowl of double wall constructioncomprising an outer wall including an annular, axially translatableportion, and an inner wall including a plurality of pivotable flapsspaced circumferentially of said inner wall, each flap having a pair ofrollers at its downstream end, a plurality of pairs of guide tracksfixed between the walls of the cowl and spaced circumferentially thereofand means for translating said annular portion axially of the cowl, andwherein said flaps have their rollers located in respective guide tracksso as to be pivoted about the rollers axes, whilst the rollers aremovable along said guide tracks so as to bodily displace said flapsaxially of the cowl.
 2. A gas turbine ducted fan engine cowl as claimedin claim 1 wherein said annular translatable portion and said flaps areinterconnected for simultaneous movement in their respective directions.3. A gas turbine ducted fan engine cowl as claimed in claim 1 whereinsaid means for translating said annular portion comprises rams.